Over the last fifteen years or so, I have investigated dozens of claims that the Gemara knew something that modern science only discovered centuries later. Initially I was very excited about such possibilities, but as I researched them, disappointment set in. In every case, I found that it was either (a) something that non-Jews in antiquity also knew, (b) something ambiguous that could be interpreted in all kinds of ways, or (c) something that is not actually true.
I am pleased to report that, finally, somebody has found something! Dr. Jeremy Brown, author of the superb book New Heavens and a New Earth: The Jewish Reaction to Copernican Thought, has launched a wonderful new blog called Talmudology. In a recent post, he discusses Rava's statement (Yevamot 97a) that delayed puberty in boys can be caused by their being either overweight or underweight. According to Dr. Brown, this has only recently been confirmed by modern science. So far, ancient sources discussing such a concept have not been found (but feel free to search!) It seems that Rava deserves credit for being the first person to state this fact.
Still, I don't think that Rava obtained this information from Sinaitic tradition, ruach hakodesh, or some talent for deriving scientific facts from Torah texts. (My reason for not believing that it was due to that is that if such possibilities were available, surely they would have been available for more significant matters, such as the basic nature of the universe, the function of different parts of the body, etc.) So how did he know it? I don't know. Perhaps it was a good intuition based on his understanding of health.
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In other news, the hot item right now in the world of Jewish scholarship is Dr. Marc Shapiro's critique of Artscroll's response regarding why they omitted portions of Rashbam's commentary to the Torah in their new Mikraos Gedolos. Artscroll justified their omission with the claim that the omitted portions were interpolations by a heretic. (This is a position that we have seen all too much of in recent years, with Rav Yitzchok Sheiner claiming that portions of Michtav Me-Eliyahu are a forgery, Rav Moshe Shapiro claiming that Rav Hirsch's letters on science are a forgery, and Rabbi Moshe Meiselman claiming that parts of R. Avraham ben HaRambam are a forgery.) Dr. Shapiro responds by pointing out that numerous Torah authorities - including one of ArtScroll's guiding mentors, Rav Yaakov Kamenetzky - discussed the passage in question, and none of them rejected it as a forgery by heretics. Make sure to read the endnotes!